1. Field of the Invention
This invention relates to personal computer systems and, more particularly, to such systems having security features enabling control over access to data retained in the system.
2. Description of the Prior Art
Personal computer systems have attained widespread use for providing computer power to many segments of today's modern society. Personal computer systems can usually be defined as a desk top, floor standing, or portable microcomputer that consists of a system unit having at least one system processor and associated volatile and non-volatile memory, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard (also known as and occasionally mentioned herein as a system board, system planar or planar) to electrically connect these components together. These systems are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses. Examples of such personal computer systems are IBM's PERSONAL COMPUTER AT and IBM's PERSONAL SYSTEM/2 Models 90 and 95.
These systems can be classified into two general families. The first family, usually referred to as Family I Models, use a bus architecture exemplified by the IBM PERSONAL COMPUTER AT and other "IBM compatible" machines. The second family, referred to as Family II Models, use IBM's MICRO CHANNEL bus architecture exemplified by IBM's PERSONAL SYSTEM/2 Models 50 through 95. Early Family I models typically used the popular INTEL 8088 or 8086 microprocessor as the system processor. Certain later Family I and the Family II models typically use the high speed INTEL 80286, 80386, and 80486 microprocessors which can operate in a real mode to emulate the slower speed INTEL 8086 microprocessor or a protected mode which extends the addressing range from 1 megabyte to 4 Gigabytes for some models. In essence, the real mode feature of the 80286, 80386, and 80486 processors provides hardware compatibility with software written for the 8086 and 8088 microprocessors.
With the growing use of personal computers in the world in recent years, more and more data or information is being collected and retained or stored in such systems. A lot of this data is sensitive in nature. In the wrong hands, data could become embarrassing to individuals, a company could lose a competitive edge, or sensitive data could be used to force payment for silence or lead to physical violence against individuals. As more users recognize the sensitive nature of data and its value, the more it becomes desirable to protect against such misuse. To protect themselves and the persons associated with the stored data, users are requiring incorporation of security and integrity features into the personal computers that they purchase.
Users are not the only people to recognize the sensitivity of the data being collected and stored. Governments are also enacting laws to enforce protection of sensitive data. One such government is that of the United States. It has recognized and responded to the gravity of the situation. The United States federal government has defined security levels and the associated requirements it takes to meet those levels, and provides a certification agency for personal computer manufacturers to submit products in order to see if the products meet the security level claimed by the manufacturer. The source for the Federal Requirements is the Department of Defense, Trusted Computer System Evaluation Criteria, DOD 5200.28 STD, 12/85, generally referred to as The Orange Book. The government has legislated that by Jan. 1, 1992 all data related to the government must only be processed and stored on personal computers with a minimum security level of C-2. For computer system hardware, the essence of the requirements is contained in the Assurance section, Requirement 6: "trusted mechanisms must be continuously protected against tampering and/or unauthorized changes . . . "
The related U.S. Pat. No. 5,388,156 describes a personal computer providing means for limiting access to certain critical data to only those users having a proper privilege to access such data. In realizing this purpose, a specialized memory element is provided for receiving and storing a Power On Password and a Privileged Access Password (sometimes hereinafter called a "POP" and a "PAP" respectively) and for coordinating the access granted to various functions and data to the activation and usage of the passwords. A user may have choices to activate or inactivate the security provisions made available, so that the system can be adapted to varying needs or desires for securing the usage of the system. The system may be adapted to the security requirements of governmental standards if desired and yet also used in an essentially unsecured manner should the circumstances of use so permit. Thus users of such systems are given great flexibility in application of the systems. Certain of the teachings of this related Application are described in detail hereinafter in view of its relationship with the invention of the present Application.